Water pre-heating arrangement

ABSTRACT

A water pre-heating arrangement, incorporating with a water heating system including a water heater, includes a heat exchanger for guiding water to flow from a water source to a water tank, and a solar energy collecting device having a solar energy collecting surface mounted to the heat exchanger wherein the solar energy collecting surface is adapted for collecting and transforming solar energy into heat energy to increase a water temperature in the heat exchanging unit so as to pre-heat the water in the heat exchanging unit before entering into the water tank. Therefore, the water heater powered by a fossil fuel heats up the water in the water tank from the pre-heated temperature to a predetermined temperature while being energy effective.

CROSS REFERENCE OF RELATED APPLICATION

This application is a Continuation-In-Part of a non-provisional application, application Ser. No. 10/393,788, filed Mar. 24, 2003.

BACKGROUND OF THE PRESENT INVENTION

1. Field of Invention

The present invention relates to a water heater, and more particularly to a water pre-heating arrangement for a water heating system, wherein the water is pre-heated by the solar energy through the water pre-heating arrangement before entering into the water heater of the water heating system so as to minimize the energy consumption of the water heater.

2. Description of Related Arts

Conventional water heaters mainly utilize gas or electricity as a power source to heat up water for domestic or industrial purpose. As shown in FIG. 1 a conventional water heating system comprises a water heater having a water outlet and a water inlet connecting with a water source in such a manner that the water at the room temperature is heated up by the water heater to reach a preset temperature.

The mechanical designs and operations of the water heater have been dramatically advanced in the past several decades due to helter-skelter technology development. However, no matter how far the conventional water heaters have advanced in regard of their operation principles, most of them still rely on conventional power source—power sources ‘conventional’ in the sense that they are artificially used for industrial or domestic purposes.

Until more recently, water heater which utilize solar energy as their power source have been developed to resolve the general problems of potential energy crises or shortages. Those solar energy heaters no doubt meet the ever-increasing demand of environmental protection and ‘clean energy source’ from people all over the world. Yet they have several drawbacks.

One trivial problem is the lack of adequate sunlight. Though, in principle, the energy source of solar energy heaters is absolutely free and unlimited, in practice, it hardly can be. Conventional solar energy heaters share a problem of expensive equipment and installation which significantly and realistically prohibits the extensive use of such environmentally friendly water heaters.

Natural limitation should be another problem. Solar energy water heaters obviously require solar energy, which is derived from sunlight. As a matter of fact, sunlight may be rare in some seasons or geographical areas. Say, for example, in some northern areas, ‘evening’ comes at 2 or 3 o'clock in the afternoon. After that, no sunlight can be obtained. Thus, in such circumstances, the solar energy water heaters cannot be used.

Back to some less extreme cases, the problem of cloudy or rainy whether may make the users of such solar energy water heaters frustrating. Bear in mind that, from engineering or scientific point of view, the specific heat capacity of water is one of the highest among popular or widely-used raw materials, especially liquid. Accordingly, in order to heat up a large amount of water for showering or bathing, a considerable amount of solar energy has to be utilized. Given the potential unstable whether condition, smooth operation of the solar energy water heaters may not be consistently achieved.

At least some better cases should be taken into account. Perhaps the above-mentioned problems in some tropical areas will be minimal, for there is substantial provision of sunlight in those places. While perhaps it can be said that there is no such problem of solar energy inadequacy in those areas, some other problems still exist.

Imagine if a given area has an adequate supply of solar energy, the whether, temperature in particular, in that area should be fairly, if not very, high. Therefore, though the problem of lack of adequate solar energy ceases to exist, at the same the demand of such solar energy water heaters ceases to be promising either. People may simply choose not to utilize hot water for shower, or the demand of hot water for showering etc. may be so low that the cost of installing the solar energy water heater can hardly be justified. Paradoxically, for conventional solar energy heaters, engineering problems conflict with marketing or economic problems.

Finally, assuming that the above mentioned problems do not exist for a given solar energy water heater, there is at least one remaining difficulty sharing among almost all solar energy water heaters, irrespective of where the heater is situated, or the method by which the heater is installed. The problem is that conventional heater of average capacity only fits for families of small size. That is to say, the conventional water heater only serves a small number of people. The underlying reason for this problem is that it is difficult to store such large amount of solar energy that it can be utilized by a lot of people, even sunlight is rich. After all, there is practical limit as to how much energy can be stored for a given solar energy collecting device.

SUMMARY OF THE PRESENT INVENTION

A main object of the present invention is to provide a water pre-heating arrangement for a water heating system, wherein the water is pre-heated by the solar energy through the water pre-heating arrangement before entering into the water heater of the water heating system so as to minimize the energy consumption of the water heater.

Another object of the present invention is to provide a water pre-heating arrangement for a water heating system, wherein the water heating system dose not require to alter its original structural design in order to incorporate with the water pre-heating arrangement so as to minimize the installation cost of the present invention.

Another object of the present invention is to provide a water pre-heating arrangement for a water heating system, which successfully provides an economic and efficient solution for pre-heating the water at a predetermined temperature by solar energy so that the water heater can effectively heat up the water into a desired water temperature by conventional power source while being energy effective.

Another object of the present invention is to provide a water pre-heating arrangement for a water heating system, wherein water is pre-heated by solar energy so that consumption of convention no-renewable energy source can be minimized.

Accordingly, in order to accomplish the above objects, the present invention provides a water pre-heating arrangement for a water heating system which comprise a water tank communicating with a water source for collecting a predetermined volume of water therefrom, and a water heater powered by a fossil fuel for heating up the water in the water tank into a predetermined temperature, comprising:

-   -   at least a heat exchanger having a heat exchanging unit, a water         inlet adapted for connecting with the water source to guide the         water to flow into the heat exchanging unit, and a water outlet         adapted for connecting with the water tank to guide the water to         flow from the heat exchanging unit to the water tank; and     -   a solar energy collecting device having a solar energy         collecting surface mounted to the heat exchanger wherein the         solar energy collecting surface is adapted for collecting and         transforming solar energy into heat energy to increase a water         temperature in the heat exchanging unit so as to pre-heat the         water in the heat exchanging unit before entering into the water         tank.

These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional water heating system.

FIG. 2 is a block diagram of a water pre-heating arrangement incorporated with a conventional water heating system according to a preferred embodiment of the present invention.

FIG. 3 is a perspective view of the water pre-heating arrangement according to the above preferred embodiment of the present invention.

FIG. 4 is a schematic diagram of a heat exchanger according to a second preferred embodiment of the present invention.

FIG. 5 is a schematic diagram of a water pre-heating arrangement according to the above second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 2 of the drawings, a water pre-heating arrangement 2 incorporates with a water heating system 1 according to a preferred embodiment of the present invention is illustrated, wherein the water heating system 1, such as a conventional water heating system, comprises a water tank 11 communicating with a water source W for collecting a predetermined volume of water therefrom, and a water heater 12 powered by a fossil fuel for heating up the water in the water tank 11 into a predetermined temperature.

The water pre-heating arrangement 2 comprises at least a heat exchanger 20 connected between the water source W and the water tank 11 and a solar energy collecting device 30 for pre-heating the water in the heat exchanger 20 before entering into the water tank 11.

The heat exchanger 20 has a heat exchanging unit 21, a water inlet 22 adapted for connecting with the water source W to guide the water to flow from the water source W to the heat exchanging unit 21 via a water incoming pipe 101, and a water outlet 23 adapted for connecting with the water tank 11 to guide the water to flow from the heat exchanging unit 21 to the water tank 11 via a water outgoing pipe 102.

The solar energy collecting device 30 has a solar energy collecting surface 301 provided on the heat exchanger 20 wherein the solar energy collecting surface 301 is adapted for collecting and transforming solar energy into heat energy to increase a water temperature in the heat exchanging unit 21 so as to pre-heat the water in the heat exchanging unit 21 before entering into the water tank 11.

According to the preferred embodiment, water at a room temperature is guided to flow from the water source W to the heat exchanging unit 21 through the water inlet 22 in such a manner that the heat exchange process can be performed in the heat exchanging unit 21 to pre-heat the water from the room temperature to a desired temperature by the solar energy.

The heat exchanging unit 21 comprises at least a heat absorbing water passage 211 extended from the water inlet 22 to the water outlet 23 for allowing the water to flow from the water source W towards the water tank 11 through the heat exchanging unit 21. As shown in FIG. 3, the heat absorbing water passage 221, having a predetermined length, recursively extended in a coiled manner to maximize a heat exchanging surface thereof. Accordingly, the heat absorbing water passage 211 is constructed in a tubular shape and made of thermally conductive material, such as metal, such that solar energy collected from the solar energy collecting device 30 can be effectively absorbed the heat absorbing water passage 211 and transferred to the water flows therethrough.

The heat exchanging unit 21 further comprises at least a heat transfer agent 212 encirclingly extended along the heat absorbing water passage 221 to enclose the heat exchanging surface thereof wherein the heat transfer agent 212 is adapted to absorb the heat energy collected from the solar energy collecting device 30 and release the heat energy to the heat absorbing water passage 211 for heating up the water flowing therethrough. The heat transfer agent 212, having a predetermined heat transfer coefficient, is thermally communicated with the solar energy collecting device 30 in such a manner that the solar energy, essentially heat energy, is arranged to be transferred to the heat transfer agent 212 which eventually raises the temperature of the heat transfer agent 212. In other words, the heat transfer agent 212 is capable of further enhancing the heat absorbing of the heat absorbing water passage 221 to pre-heat the water flowing therethrough.

From simple heat transfer theory, since the temperature of the water flowing through the heat absorbing water passage 211 is normally lower than the temperature of the heat transfer agent 212, the heat energy carried by the heat transfer agent 212, derived from the solar energy collecting device 30, will be transferred to the water flowing through the heat absorbing water passage 211 via the heat exchanging surface thereof, such that the water flowing from the water inlet 22 is preheated to a predetermined temperature by the heat transfer agent 212 before reaching the water outlet 23. For better heat transfer performance, the heat transfer agent 212 should be circulated within the heat exchanging unit 21 with a flowing direction opposite to the flowing direction of the water through the heat absorbing water passage 211.

It is worth to mention that several factors are of crucial importance in determining the heat transfer between the heat transfer agent 212 and the water within the heat absorbing water passage 211. In short, physical parameters such as the diameter of the heat absorbing water passage 211, the flow rate of the water within the heat absorbing water passage 211, the thickness of the wall of heat absorbing water passage 211, and the thermal conductivity of the material by which the heat absorbing water passage 211 is made all determine the heat transfer effectiveness and efficiency between the heat transfer agent 212 and the water within the heat absorbing water passage 211.

The solar energy collecting device 30 comprises a supporting plate 31 mounted to the heat exchanging unit 21 wherein the solar energy collecting surface 301 is provided on the supporting plate 31 for absorbing radiation as the solar energy from the sunlight. Accordingly, the solar energy collecting surface 301 is arranged for being orientated to face towards the sunlight for heat absorption. The solar energy collecting device 30 is preferred to locate on top of a house or a building so that the solar energy collecting surface 301 can substantially expose to the sunlight and is capable of collecting a large amount of solar energy. In addition, the supporting plate 31 can be selectively adjusted to maximize the exposure of the solar energy collecting surface 301 with respect to the sunlight, so that the user is able to adjustably orientate the solar energy collecting device 30 to obtain a better result of the water preheating process.

Alternatively, the solar energy collecting surface 301 of the solar energy collecting device 30 is directly formed on an outer surface of the heat absorbing water passage 211 of the heat exchanging unit 21 such that the heat absorbing water passage 211 can be directly absorbing the heat from the sunlight to transfer the heat to the water while the water flows through the heat absorbing water passage 211. Accordingly, the heat absorbing water passage 211 can be, for example, an all-glassed evacuated solar collector tube, wherein the heat absorbing water passage 211 directly collects the solar energy. In other words, the heat absorbing water passage 211 also embodies as the solar energy collecting device 30 to simplify the structure of the water pre-heating arrangement, so as to minimize the manufacturing cost of the present invention.

It is worth to mention that the power per unit surface area of the solar energy collecting surface 301 in the sun's radiation (before the sunlight passes through the earth's atmosphere) is about 1.4 kW/m². A maximum of about 1.0 kW/m² reaches the surface of the earth on a clear day, and the time average, over a 24-hour period, is about 0.2 kW/m². Therefore, the solar energy collected by the solar energy collecting device 30 is capable of pre-heating the water to a pre-heated temperature which is higher than the room temperature.

As shown in FIG. 1, the water pre-heating arrangement 2 further comprises a water reservoir 40 arranged for storing the water pre-heated from the heat exchanger 20, wherein the water reservoir 40 has a water entrance 41 operatively connected to the water outlet 23 of the heat exchanger 20 via a water transferring pipe 401 and a water exit 42 adapted for connecting to the water outgoing pipe 102 of the water tank 11 so as to guide the water to flow to the water tank 11. Accordingly, the water, which is pre-heated at the heat exchanger 20, flows out of the water outlet 23 through the water transferring pipe 401 and is temporary stored in the water reservoir 40, wherein the water reservoir 40 has a heat insulated layer 43 for minimizing heat loss of the water in the water reservoir 40 to the surroundings. The heat insulated layer 43 can be a fiber glass insulating layer formed at an outer and/or inner side of the water reservoir 40 as an outer and/or inner casing thereof to prevent heat loss of the water stored in the water reservoir 40.

The water pre-heating arrangement 2 further comprises means 50 for controlling the water out-flowing from the heat absorbing water passage 211 towards the water tank 11 through the water reservoir 40. According to the preferred embodiment, the controlling means 50 is a one-way control valve 51 connected to the water exit 42 of the water reservoir 40 wherein the control valve 51 of the controlling means 50 is capable of determining a water level of the water tank 11 for allowing the water to flow from the water reservoir 40 to the water tank 11 so as to control the water flow from the heat absorbing water passage 211 towards the water tank 11. Accordingly, when the water in the water tank 11 drops to a predetermined water level, the control valve 51 automatically opens for refilling the water from the water reservoir 40 to the water tank 11. However, when the water tank 11 is full of water, the control valve 51 automatically closes to stop the water flowing to the water tank 11. Therefore, the control valve 51 of the controlling means 50 is considered as a safety valve to retain a predetermined volume of water in the water tank 11. It is worth mentioning that the heat absorbing water passage 211 can function as the water reservoir 40 for directly flowing the water towards water tank 11 such that the water reservoir 40 is optionally installed into the water-preheating arrangement 2.

It is also worth mentioning that when both the water reservoir 40 and the water tank 11 are full of water, the control valve 51 of the controlling means 50 will be closed to stop the water to flow from the water reservoir 40 to the water tank 11 wherein the water in the water reservoir 40 will remain in its pre-heated temperature and will flow to the water tank 11 once the control valve 51 opens.

The pre-heating arrangement 2 further comprises a water regulating circuitry 60 which comprises a water pipeline 61 having a water inlet end 611 adapted for connecting to the water source W and a water outlet end 512 adapted for connecting to the water tank 11, and a regulating valve 62 operatively connected to the water pipeline 61 for controlling the water to flow from the water source W to the water tank 11 through the water pipeline 61. Accordingly, the regulating valve 62 is a temperature detecting valve for detecting the temperature of the water in the water reservoir 40 wherein when the temperature of the water in the water reservoir 40 is higher than the water at a room temperature, the regulating valve 62 is closed to block the water directly flowing from the water source W to the water tank 11 through the water pipeline 61. Once the temperature of the water in the water reservoir 40 is lower than the water at the room temperature, the regulating valve 62 will be opened to allow the water directly flowing from the water source W to the water tank 11 through the water pipeline 61. It is because the water heater 12 requires less energy to increase the water from the room temperature to the predetermined temperature.

Furthermore, the water regulating circuitry 60 is constructed as a safety circuitry wherein when no water flows into the heat exchanger 20, i.e. no water is stored in the water reservoir 40, the regulating valve 62 will automatically open to allow the water filling into the water tank 11 so as to ensure the water in the water tank 11 reaching the predetermined water level and the normal operation of the water heater 12 to heat up the water in the water tank 11.

According to the preferred embodiment, the water heater 12 is a conventional gas water heater or electric water heater powered by gas or electricity respectively. Since the water is pre-heated at the water pre-heating arrangement 2 through the solar energy to reach the pre-heated temperature, the water heater 12 can save its energy to increase the water from the pre-heated temperature to the predetermined temperature. Even though there is insufficient sunlight at some geographical areas to efficiently heat up the water from the room temperature to the predetermined temperature, the water will pre-heat to reach the pre-heated temperature, which is higher than the room temperature, to save the energy consumption of the water heater 12.

It is worth to mention that the water pre-heating arrangement 2 can be simply incorporated with the conventional water heating system 1 by connecting the water incoming pipe 101 of the water source W to the water inlet 22 of the heat exchanger 20 and the water outgoing pipe 102 of the water tank 11 to the water exit 42 of the water reservoir 40. Therefore, the water heating system does not require altering its original structural design so as to minimize the installation cost of the water heating system incorporating with the water pre-heating arrangement 2.

From the forgoing analysis, one skilled in the art can easily discover that the present invention provides a convenient and simple water heater which jointly utilize solar energy and conventional fossil fuel. The requirement of obtaining a large, if not unrealistic, amount of solar energy ceases to exist because the present invention does not simply require heating up the water solely by solar energy. At the same time, solar energy plays a vital role in the present water heating system, thereby achieving the object of saving non-renewable energy source.

Referring to FIG. 4 to FIG. 5 of the drawings, a water pre-heating arrangement 2′ incorporates with a water heating system 1′ according to a second preferred embodiment of the present invention is illustrated, wherein the water heating system 1′, such as a conventional water heating system, comprises a water tank 11′ for collecting a predetermined volume of water, and a water heater 12′ powered by a fossil fuel for heating up the water in the water tank 11′ into a predetermined temperature.

The water pre-heating arrangement 2′ comprises at least a heat exchanger 20′ connected between the water source W′ and the water tank 11′, and a solar energy collecting device 30′ for pre-heating the water in the heat exchanger 20′ before entering into the water tank 11′. Thus, the water tank 11′ communicates with the water source W through the heat exchanger 20′ for pre-heating.

The heat exchanger 20′ has a heat exchanging unit 21′ for converting solar energy to heat energy which is to be utilized for pre-heating water in the water tank 11′, and a water reservoir 24′ which comprises a water storing unit 241′ communictaed with the water source W though a water inlet and the water tank 11′, and a heater transfer module 242′ thermally communicated with the water storing unit 241′. Thus, water at room temperature from the water source W is stored in the water storing unit 241′ for pre-heating by the heater transfer module 242′ before it is drained to the water tank 11′ though a water outlet for normal use.

The heat exchanger 20′ further comprises a heat exchange agent 201′ flowing between the heat exchanging unit 21′ and water reservoir 24′. The heat exchange agent 201′ is embodied as having a predetermined heat conductivity so as to effectively retrieve heat energy collected by the solar energy collecting device 30′ and transfer it to the heater transfer module 242′ which in turn heats up the water stored in the water storing unit 241′.

The solar energy collecting device 30′ has a solar energy collecting surface 301′ mounted to the heat exchanger 20′ wherein the solar energy collecting surface 301′ is adapted for collecting and transforming solar energy into heat energy to increase the temperature of the heat transfer agent in the heat exchanging unit 21′.

According to the second preferred embodiment, the solar energy collecting device 30′ comprises a plurality of heat conversion tubes 31′ which are integrally mounted together in such a manner that the outer surfaces of the heat conversion tubes 31′ define the solar energy collecting surface 301′. Each of the heat conversion tubes 31′ comprises an outer glass evacuated tube 311′, and a heat transfer pipe 312′, which is preferably embodied as a copper pipe, embedded within the glass evacuated tube 311′ and extended to communicate with the heat exchanging unit 21′ for transferring heat collected from the heat transfer pipe 312′ to the heat transfer agent 201′ flowing through the heat exchanging unit 21′.

Specifically, the heat exchanging unit 21′ comprises a heat transfer housing 211′ and a fluid passageway 212′ extended therein, wherein the heat transfer agent 201′ is arranged to flow through the fluid passageway 212′ from the heater transfer module 242′ for retrieving energy from the heat conversion tubes 31′ and then transfer the heat energy received back to the heater transfer module 242′ where the heat is further transferred to the water storing unit 241′ for pre-heating the water stored therein.

Accordingly, the fluid passageway 212′ in the heat exchanging unit 21′ is thermally communicated with the heat conversion tubes 31′ inside the heat exchanging unit 21′ such that the solar energy collected would be transferred to the heat exchange agent through the fluid passageway 212′.

Moreover, the heat exchanging unit 21′ further comprises heat insulating materials 213′ filled within the heat transfer housing 211′ so as to minimize heat loss from the heat transfer agent 201′ to the surrounding environment, especially when water pre-heating arrangement is working in a cold environment.

When sunlight reaches the glass evacuated tubes 311′, the solar energy would be trapped within the glass evacuated tubes 311′ in such a manner that it is then transformed into heat energy which raises the temperature of the heat transfer pipe 312′. As a result, from simple heat transfer theory, heat energy in the heat transfer pipe 312′ would then transferred to the heat transfer agent within the heat exchanging unit 21′. The heat transfer agent is then transported to the heater transfer module 242′ wherein the water in the water reservoir 24′ would be heated up by the heat transfer agent having the elevated temperature.

The heat transfer agent is preferably embodied as non-toxic, bio-degradable propylene glycol solution which is capable of transferring heat from the heat transfer pipe 312′ to the heater transfer module 242′.

From the forgoing descriptions, it is anticipated that since the freezing point of the heat transfer agent can be as low as below zero, the present invention would still be effectively utilized in very cold ambient temperature for pre-heating water stored in the water storing unit 241′, as long as there is adequate sunlight collectable by the solar energy collecting device 30′.

Moreover, the heat exchanger 20′ may further comprises, as in the first preferred embodiment, an insulating layer surrounding the water storing unit 241′ so as to minimize heat loss stored in that water storing unit 241′.

One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

It will thus be seen that the objects of the present invention have been fully and effectively accomplished. It embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure form such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims. 

1. A water pre-heating arrangement for a water heating system which comprises a water tank for collecting a predetermined volume of water, and a water heater powered by a fossil fuel for heating up said water in said water tank into a predetermined temperature, wherein said water pre-heating arrangement comprises: a solar energy collecting device having a solar energy collecting surface which is adapted to collect solar energy and transform said solar energy into heat energy; and a heat exchanger which is connected between said water heating system and said solar energy collecting device, and comprises a heat exchanging unit communicating with said solar energy collecting device for receiving said heat energy therefrom, and a water reservoir which stores said water from said water source, and transfer said heat energy received by said heat exchanging unit to said water so as to pre-heat said water into a predetermined temperature to supply to said water heating system.
 2. The water-preheating arrangement, as recited in claim 1, wherein said water reservoir of said heat exchanging unit comprises a water storing unit communicated with said water source to store said water therein, and a heat transfer module thermally communicated between said water storing unit and said heat exchanging unit in such a manner that said water from said water source is stored in said water storing unit for pre-heating by said heater transfer module before said water is drained to said water tank.
 3. The water-preheating arrangement, as recited in claim 2, wherein said heat exchanger further comprises a heat exchange agent, having a predetermined heat conductivity, flowing between said heat exchanging unit and said water reservoir, and arranged to effectively retrieve heat energy collected by said solar energy collecting device so as to transfer said solar energy to said heater transfer module for heating up said water stored in said water storing unit.
 4. The water pre-heating arrangement, as recited in claim 3, wherein said solar energy collecting device comprises a plurality of heat conversion tubes integrally mounted together such that outer surfaces of said heat conversion tubes define said solar energy collecting surface, wherein each of said heat conversion tubes comprises an outer glass evacuated tube and a heat transfer pipe embedded within said respective glass evacuated tube and extended to communicate with said heat exchanging unit, wherein sunlight is collected by said glass evacuated tube and stored as heat energy by said heat transfer pipe for transferring heat collected from said heat transfer pipe to said heat transfer agent flowing through said heat exchanging unit.
 5. The water pre-heating arrangement, as recited in claim 3, wherein said heat transfer agent is non-toxic, biodegradable propylene glycol solution which is capable of transferring heat from said solar energy collecting device to said water reservoir, while said heat transfer agent has a freezing point lower than that of said water such that said water pre-heating arrangement is capable of pre-heating said water in said water storing unit under an ambient temperature below zero Celsius degree.
 6. The water pre-heating arrangement, as recited in claim 4, wherein said heat transfer agent is non-toxic, biodegradable propylene glycol solution which is capable of transferring heat from said solar energy collecting device to said water reservoir, while said heat transfer agent has a freezing point lower than that of said water such that said water pre-heating arrangement is capable of pre-heating said water in said water storing unit under an ambient temperature below zero Celsius degree.
 7. The water pre-heating arrangement, as recited in claim 5, wherein said heat exchanging unit comprises a heat transfer housing and a fluid passageway extended therein, wherein said heat transfer agent is arranged to flow through said fluid passageway from said heat transfer module for retrieving said energy from said heat conversion tubes and transferring said heat energy received to said heat transfer module where said heat is further transferred to said water storing unit for pre-heating said water stored therein.
 8. The water pre-heating arrangement, as recited in claim 6, wherein said heat exchanging unit comprises a heat transfer housing and a fluid passageway extended therein, wherein said heat transfer agent is arranged to flow through said fluid passageway from said heat transfer module for retrieving said energy from said heat conversion tubes and transferring said heat energy received to said heat transfer module where said heat is further transferred to said water storing unit for pre-heating said water stored therein.
 9. The water pre-heating arrangement, as recited in claim 7, wherein said heat exchanging unit further comprises heat transfer materials filled within said heat transfer housing for minimizing heat loss from said heat transfer agent to surrounding so as to ensure maximum efficiency of heat transfer between said heat exchanging unit and said water storing unit.
 10. The water pre-heating arrangement, as recited in claim 8, wherein said heat exchanging unit further comprises heat transfer materials filled within said heat transfer housing for minimizing heat loss from said heat transfer agent to surrounding so as to ensure maximum efficiency of heat transfer between said heat exchanging unit and said water storing unit.
 11. A water heating system, comprising: a water tank for collecting a predetermined volume of water from a water source; a water heater powered by a fossil fuel for heating up said water in said water tank into a predetermined temperature; and a water pre-heating arrangement, which comprises: a solar energy collecting device having a solar energy collecting surface which is adapted to collect solar energy and transform said solar energy into heat energy; and a heat exchanger which is connected between said water heating system and said solar energy collecting device, and comprises a heat exchanging unit communicating with said solar energy collecting device for receiving said heat energy therefrom, and a water reservoir which stores said water from said water source, and transfer said heat energy received by said heat exchanging unit to said water so as to pre-heat said water into a predetermined temperature to supply into said water heating system.
 12. The water heating system, as recited in claim 11, wherein said water reservoir of said heat exchanging unit comprises a water storing unit communicated with said water source to store said water therein, and a heat transfer module thermally communicated between said water storing unit and said heat exchanging unit in such a manner that said water from said water source is stored in said water storing unit for pre-heating by said heater transfer module before said water is drained to said water tank.
 13. The water heating system, as recited in claim 12, wherein said heat exchanger further comprises a heat exchange agent, having a predetermined heat conductivity, flowing between said heat exchanging unit and said water reservoir, and adapted to effectively retrieve heat energy collected by said solar energy collecting device so as to transfer said solar energy to said heater transfer module for heating up said water stored in said water storing unit.
 14. The water heating system, as recited in claim 13, wherein said solar energy collecting device comprises a plurality of heat conversion tubes integrally mounted together such that outer surfaces of said heat conversion tubes define said solar energy collecting surface, wherein each of said heat conversion tubes comprises an outer glass evacuated tube and a heat transfer pipe embedded within said respective glass evacuated tube and extended to communicate with said heat exchanging unit, wherein sunlight is collected by said glass evacuated tube and stored as heat energy by said heat transfer pipe for transferring heat collected from said heat transfer pipe to said heat transfer agent flowing through said heat exchanging unit.
 15. The water heating system, as recited in claim 13, wherein said heat transfer agent is non-toxic, biodegradable propylene glycol solution which is capable of transferring heat from said solar energy collecting device to said water reservoir, while said heat transfer agent has a freezing point lower than that of said water such that said water pre-heating arrangement is capable of pre-heating said water in said water storing unit under an ambient temperature below zero Celsius degree.
 16. The water heating system, as recited in claim 14, wherein said heat transfer agent is non-toxic, biodegradable propylene glycol solution which is capable of transferring heat from said solar energy collecting device to said water reservoir, while said heat transfer agent has a freezing point lower than that of said water such that said water pre-heating arrangement is capable of pre-heating said water in said water storing unit under an ambient temperature below zero Celsius degree.
 17. The water heating system, as recited in claim 15, wherein said heat exchanging unit comprises a heat transfer housing and a fluid passageway extended therein, wherein said heat transfer agent is arranged to flow through said fluid passageway from said heat transfer module for retrieving said energy from said heat conversion tubes and transferring said heat energy received to said heat transfer module where said heat is further transferred to said water storing unit for pre-heating said water stored therein.
 18. The water heating system, as recited in claim 16, wherein said heat exchanging unit comprises a heat transfer housing and a fluid passageway extended therein, wherein said heat transfer agent is arranged to flow through said fluid passageway from said heat transfer module for retrieving said energy from said heat conversion tubes and transferring said heat energy received to said heat transfer module where said heat is further transferred to said water storing unit for pre-heating said water stored therein.
 19. The water heating system, as recited in claim 17, wherein said heat exchanging unit further comprises heat transfer materials filled within said heat transfer housing for minimizing heat loss from said heat transfer agent to surrounding so as to ensure maximum efficiency of heat transfer between said heat exchanging unit and said water storing unit.
 20. The water heating system, as recited in claim 18, wherein said heat exchanging unit further comprises heat transfer materials filled within said heat transfer housing for minimizing heat loss from said heat transfer agent to surrounding so as to ensure maximum efficiency of heat transfer between said heat exchanging unit and said water storing unit. 